The damaging effects of sunlight on skin are well documented. Contrary to what most people believe, it is not necessary that one sunbathe to suffer the ill-effects of excessive UV exposure. In fact, a lot of damage can be done just by routine day-to-day activities in the sunlight. Some scientists estimate that over 70 percent of the damage the sun inflicts on the average person's skin over a lifetime is the result of simply being outdoors or even sitting by a window.
The major short term hazard of prolonged exposure to sunlight is erythema (i.e., sunburn). The 290 to 320 nanometer wavelength ultraviolet radiation range, designated as the "UVB" wavelength range, tends to be the primary cause of erythema. The 320 to 400 nanometer wavelength ultraviolet radiation range, designated as the "UVA" wavelength range, also produces erythema.
In addition to the short term hazard or erythema, there are also long term hazards associated with UV radiation exposure. One of these long term hazards is malignant changes in the skin surface. Numerous epidemiologic studies demonstrate a strong relationship between sunlight exposure and human skin cancer.
Another long term hazard of ultraviolet radiation is premature aging of the skin. This condition is characterized by wrinkling and yellowing of the skin, along with other physical changes such as cracking, telangiectasis (spider vessels), solar keratoses (growths), ecchymoses (subcutaneous hemorrhagic lesions), and loss of elasticity (sagging). The adverse effects associated with exposure to UVA and UVB wavelength radiation are more fully discussed in DeSimone, "Sunscreen and Suntan Products", Handbook of Nonprescription Drugs, 8th Ed., Chapter 26, pp. 533-546 (American Pharmaceutical Association, Washington, D.C.; 1986); Grove and Forbes, "A Method for Evaluating the Photoprotection Action of Sunscreen Agents Against UV-A Radiation", International Journal of Cosmetic Science, 4, pp. 15-24 (1982); and U.S. Pat. No. 4,387,089, DePolo, issued Jun. 7, 1983; the disclosures of all of which are incorporated herein by reference in their entirety. Hence, although the immediate effects of ultraviolet radiation may be cosmetically and socially gratifying, the long-term hazards are cumulative and potentially serious.
The fact that these effects are taken seriously by the general public is suggested by considering the sun protection products market. This market has grown considerably in recent years and many new products are introduced each year. What used to be looked upon as a seasonal business is no longer. Sun protection compounds are now included in a diversity of personal care products, particularly cosmetic-type products which are worn on a daily basis.
The most common agents for sun protection are sunscreens. These agents exert their effect through chemical means, i.e., they absorb ultraviolet radiation so that it cannot penetrate the skin. More and more consumers are interested in using products which contain sunscreen agents, but are both more sun protective and more cosmetically appealing.
U.S. Pat. Nos. 4,847,267, issued Jul. 11, 1989 and 4,742,066, issued May 3, 1988, both to Deckner et al., relate to skin treatment compositions which inhibit generation of free radicals in the skin. Optional components for use in these compositions include skin conditioning agents (including allantoin and panthenol), ultraviolet absorbing agents, and vitamins such as Vitamin E.
U.S. Pat. No. 4,833,259, issued May 23, 1989, to Erlemann et al., describes sunscreen agents which are esters of p-methoxycinnamic acid with d,l-alpha-tocopherol, pantolactone or panthenol. Allantoin, Vitamin E acetate and panthenol are optional components exemplified therein.
U.S. Pat. No. 4,743,442, issued May 10, 1988, to Raaf et al., describes skin care compositions containing mineral salts. Optional components include substances for absorbing UV-radiation, Vitamin E, panthenol, and allantoin.
U.S. Pat. No. 4,737,360, issued Apr. 12, 1988, to Allen et al., describes skin care compositions comprising a pollen extract and non-animal and non-mineral oils. Optional components are said to include UV screens. Example 4 describes a deep cleaning milk containing tocopherol, allantoin, and DL-panthanol.
U.S. Pat. No. 4,603,046, issued Jul. 29, 1986, to Georgalas et al., relates to skin treatment compositions, such as sunscreen compositions, which include a tri(dihydroxyalkyl)rutoside as a UV-A absorber and moisturizer. Optional components for use in these compositions include skin conditioning agents (including allantoin and panthenol), ultraviolet absorbing agents, and vitamins such as Vitamin E.
It is an object of the present invention to provide topical compositions which will prevent acute (erythema) and chronic (photoaging) effects of exposure to the sun. An object is also to increase the photoprotectiveness of highly photoprotective sunscreen compositions via a non-sunscreen mechanism. It is a further object to provide cosmetically-acceptable compositions which further enhance the sun protective benefit provided by sunscreen actives and, if desired, still permit tanning of the skin to occur. An additional object is to provide an inexpensive and safe way to increase the photoprotectiveness of highly photoprotective sunscreen compositions and, if desired, thereby use lower concentrations of sunscreen agents. Finally, an object is to provide sunscreen compositions which have better consumer acceptance and/or are more soothing to the skin.
These and other objects of the present invention will become readily apparent from the detailed description which follows.
All percentages and ratios used herein are by weight, and all measurements made at 25.degree. C., unless otherwise specified.